This invention relates to a circuit for monitoring temperatures of electrical switching devices, and in particular the temperature of the contacts in circuit breakers.
As with most equipment used in the electrical field, temperature is a limiting factor in the life expectancy of circuit breakers. If temperatures in excess of those for which the circuit breakers have been designed are reached, the insulation used in the circuit breaker degrades, and deterioration of the contacting members (i.e. contacts) occurs. By monitoring the temperature of a circuit breaker, appropriate action can be taken to ensure that the temperature of the circuit breaker does not exceed the design (or rated) limits.
Direct measurement of the temperature of the contacts of a circuit breaker is not always possible, particularly when high voltages are involved and the integrity of the circuit breaker insulation must be maintained. Accordingly, some type of indirect temperature monitoring must be devised to handle situations of this type. It is an object of the present invention to provide means for indirectly monitoring the temperature of electrical switching devices.